Sound waves are sound waves are
(a) transverse waves characterized by the displacement of air molecules.
(b) longitudinal waves characterized by the displacement of air molecules.
(c) longitudinal waves characterized by pressure differences.
(d) both (b) and (c). (e) (a), (b) and (c).

(c) longitudinal waves characterized by pressure differences.

Explanation:

Sound waves are longitudinal waves which can travel through the medium in such a way that medium molecules will oscillate in the direction parallel to the direction of propagation of wave

So here we can say that medium molecules will oscillate in such a way that at few positions all the molecules comes closer and known as compression where pressure becomes maximum

While other points are those in which the pressure is minimum where molecules moves far apart known as rarefaction

So correct answer will be

(c) longitudinal waves characterized by pressure differences.

the current is 0.6

voltage ÷ resistance = current

so 12 ÷ 20 = 0.6

f=ma newton

f=100x2.5=250n